Ground termination with dampened resonance

ABSTRACT

A system of dampening resonance is provided. In an embodiment, ground traces may be coupled to a common or ground plane via dampening elements such as resistors a predetermined distance from a non-dampened coupling. Ground terminals in a connector have with a separated electrical length that allows for a potential to exist between the ground terminal and a common ground. When the ground terminals are coupled to the ground traces, the dampening element, which may be a resistor, helps convert energy traveling over ground terminal into heat, thus reducing or preventing resonance conditions in the connector.

REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 12/918,898, filed Jan. 18, 2011, now U.S. Pat. No. 8,614,398, whichis incorporated herein by reference in its entirety and claims priorityto PCT Application No. PCT/US2009/051409, filed Jul. 22, 2009, which inturn claims priority to Provisional Application Ser. No. 61/082777,filed Jul. 22, 2008, which is incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION

Connectors are used in a variety of electronic devices and many of thesedevices are data-transfer devices that are used to transmit data at datarates of 1 Gbps and higher. Cable assemblies are used to connect two ormore devices together and it is desirable to maintain a continuity ofimpedance through the cable assembly and the mating interface becauseimpedance mismatches and discontinuities can create signal reflectionsthat generate noise. Electrical cables and printed circuit boards areexamples of structures that can include single, continuous grounds inthe form of, for example, a large ground plane in a circuit board or anextensive shield in a cable. One benefit of such a shared ground planeis that a common mode corresponding to each signal transmission line hasa common voltage (e.g., the difference in potential between the groundassociated with one signal pair and the ground associated another signalpair at a particular point along the transmission path is zero).

However, when a circuit board is coupled to a connector, the commonalityof the ground structure is lost in the connector because each signalpair is usually associated with a different ground terminal within theconnector. Because of different energies due to variations in the commonmode for each signal path, when the various grounds are rejoined, theyeach will tend to have a different voltage and the differences willcause noise to be transmitted along the transmission line.

For example, many board connectors often include two grounds terminalsthat lie on opposing sides of a differential pair of signal terminals.Each ground terminal can have a different potential due to its positionwith respect to the differential pair. The potential on each groundterminal can also be affected based on the position of other signalpairs. As such, each ground terminal tends to have a different potentialonce separated. When these ground terminals are joined again (e.g., areterminated to a common ground plane), the difference in potentialcreates an energy wave that can reflect through the connector (creatingnoise on the signal transmission pairs). As the frequency of the energywave created by the discontinuity in potential increases, the wavelength of the frequency of the energy wave created by the voltagepotential can approach the separated electrical length of the groundterminal, in which case the wave energy will tend to create a resonancethat can significantly add to the noise level for the frequency ofinterest.

The resonance occurs in what is known as a “resonant cavity” and theboundaries of this resonant cavity can be equated with the separateelectrical length of the terminal from a first point where the groundterminal is no longer associated with a single, continuous (e.g.,shared) ground but is instead separate and thus can have a potentialcompared to other ground terminals. A region that forms the separateelectrical length is where the potential imbalance occurs and this isalso where resonance can occur. The noise resulting from the resonanceleads to degradation in signal integrity. As can be appreciated,shortening the connector can also help shorten the electrical length,thus helping to diminish the effect of higher frequencies, but asfrequencies increase, shortening the connector becomes less and lesseffective or practical. Therefore, certain people would appreciateconnector system that could function at higher frequencies.

SUMMARY OF THE INVENTION

In an embodiment, a connector with a paddle card is provided where thepaddle card includes a first and second end and a first and secondsignal trace that are separate on the first end of paddle card and arejoined at a common area which is positioned toward the second end.Positioned between the first and second signal trace is a third signaltrace that extends to the common area. The first and second signal traceare coupled to the third signal trace via a first and second dampeningelement with the dampening elements positioned a predetermined distancefrom the common area. The dampening elements may be resistive elements.

In another embodiment, a circuit board and connector system is provided.The connector includes a first and second ground terminal The first andsecond ground terminals have a maximum separated electrical length. Theconnector is coupled to the circuit board and the circuit board includea first ground trace that is coupled to the first ground terminal and asecond ground trace that is coupled to the second ground terminal Thefirst and second ground traces separately extend to a common area on thecircuit board and the first and second ground traces are joined at thecommon area. Positioned between the first and second signal trace is athird ground trace and the third ground trace also extends to the commonarea. At a predetermined distance from the common area, the first andsecond ground trace are coupled to the third ground trace via dampeningelements. The predetermined distance can be configured so that it isequivalent to an electrical length that is a fraction of the maximumseparated electrical length of the terminals. The terminals may becoupled to the signal traces via surface mount technology or viathru-hole technology.

BRIEF DESCRIPTION OF THE DRAWINGS

In the course of this detailed description, reference will be frequentlymade to the attached drawings in which:

FIG. 1 is a schematic view of a connector system illustrating electricallengths of conductive elements positioned therein.

FIG. 1A illustrates a diagram of the connector depicted in FIG. 1.

FIG. 2 is an isometric partially exploded view of an embodiment of aconnector system.

FIG. 3 is an exploded view of a cable connector depicted in FIG. 2.

FIG. 3A is an enlarged detail view of an embodiment of a partialconnector system that includes a paddle card mating with terminals.

FIG. 3B is a top plan view of the paddle card shown in FIG. 3.

FIG. 4 is a perspective view of an embodiment of a paddle card that hasa resonance damping structure integrated therein.

FIG. 5A is an exploded view of the paddle card of FIG. 4.

FIG. 5B is the same view as FIG. 5A, but with the resonance dampingelements exploded thereon for clarity purposes.

FIG. 6 is an enlarged detail view of the end of the circuit carddepicted in FIG. 4.

FIG. 7 is a perspective view of another embodiment of a connectormounted to a circuit board, as viewed from below.

FIG. 8 is a partially exploded view of FIG. 7, taken from above theconnector and circuit board and illustrating the connector partiallyspaced apart from the circuit board.

FIG. 9A is a perspective view of the underside of the circuit boarddepicted in FIG. 7.

FIG. 9B is a partially exploded view of the embodiment depicted in FIG.9A.

FIG. 9C is a bottom plan view of the circuit board depicted in FIG. 7.

FIG. 9D is a diagrammatic view of a connector terminal with a surfacemount tail attached to a contact pad and illustrating the electricallength Lc for such a connector terminal.

FIG. 9E is the same view as FIG. 9D but for a connector terminal with athrough hole tail.

FIG. 10 is a perspective view of another embodiment of a connectorsystem.

FIG. 10A is a partially exploded view of the system depicted in FIG. 10.

FIG. 10B is an exploded view of the connector depicted in FIG. 10.

FIG. 10C is a perspective view of a cross-section of the connectorsystem depicted in FIG. 10.

FIG. 11 is a perspective view of the circuit board depicted in theconnector system of FIG. 10.

FIG. 12 is a schematic cross-section of an embodiment of a circuitboard.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before discussing certain features it detail, it should be noted thatthe features provided below may be used in combination with otherfeatures. Accordingly, this application is not intended to be limited tothe depicted combinations but instead is intended to include additionalcombinations that would be appreciated as alternatives by a person ofskill in the art, even if the particular combination is not expresslydepicted or discussed herein.

In an embodiment, a circuit board is provided that can be used withcable assemblies and board-mounted connectors for controlling resonanceoccurring within the resonant cavity of the connector system at theconnector and circuit card/circuit board level by conditioning thegrounds on the circuit card or board. The open-ended ground members areconnected, or shorted, together proximate to the openings by individualdampening elements, preferably resistors. The resistors provide a meansfor absorbing some of the energy caused by a variation in the voltagepotential of separate ground terminals. The resistors serve to conditionthe grounds in the paddle card and placement of the resistors near theboundary between the connectors and sufficiently far enough from acommon area helps ensure that the resonant energy is reliably dampened.

Another embodiment includes a paddle card for use with a cable assemblyin which the paddle card incorporates a plurality of ground membersextending within a common plane, one of the ground members being aprimary ground path and the other ground member being a secondary path,the two paths being shorted together by one or more resistive elementsthat dissipate energy. The two paths are joined together in a commonarea. The distance of the one or more resistive elements from the commonarea can be configured to correspond to at least a fraction of aseparated electrical length of a terminal in a mating connector.

FIG. 1 illustrates a schematic representation of an exemplary connectorsystem. A board 5 supports a connector 10. A plurality of terminals 12are positioned in the connector 10 and electrically couple the board 5to a connector 15. The connector 15 supports an edge card 17 and whenthe connector 15 is mated to the connector 10, contacts on the edge card17 are electrically coupled to the terminals 12. Wires 22 in cable 20are mounted to the edge card 17 and allow signals from the board 5 to betransmitted to another location (e.g., a different board not shown).

FIG. 1A is a schematic diagram that illustrates additional features ofthe system depicted in FIG. 1. A circuit board 5 is electrically coupledto terminals 12 in connector 10 and the terminals 12 are electricallycoupled to the paddle card 17, which is electrically coupled to wires 22in the cable 20. This allows the S+ and S− terminals to send a signalthrough the system using differential signally. While it would be idealto have only differential signaling, in practice it tends to bebeneficial to include a ground plane to help shield the signals. Theproximity of the signal pair and the ground therefore creates a commonmode signal that traverses the ground. In locations where the ground isshared (such as in the board 5 and cable 20), the electrical structurecan have a common continuous ground to which the signal traces or wirescan use as a reference and return. Similarly, the connector 15 can alsoinclude a paddle card with a shared or commoned ground. One problem withdoing so, however, is that the points between the location where thegrounds are separated provides an electrical length where potentialsbetween two grounds can vary. This variance in potential can create aresonance cavity. In particular, the separate grounds could each have apotential with respect to each other and this variation in potential cancreate a standing signal wave on the grounds and therefore causeundesired noise on the signal pair.

Typically the junction between the board 5 and the paddle card 17 iswhere the ground is split onto multiple terminals 12. It has beendetermined that the separated electrical length of the ground terminalscan act to form a resonance chamber for signaling frequencies that havea wavelength that approaches the separated electrical length. As can beappreciated, if the resonance is not dampened, the resulting standingwave can be significant.

FIG. 2 illustrates a cable connector 100 that can be used to mate with aboard connector 102, so named because it is mounted on a circuit board104 that is mounted within an electronic device 106, such as a server,router, memory storage or the like. The connector 100 typically includesa cable 108 that houses a plurality of signal transmission wires 109,with pairs of such wires making up respective differential signaltransmission pairs. The wires 109 can be enclosed within a continuousmetal shield 110 that extends around the wires 109. The wires 108 areindividually terminated (termination not shown) to circuit tracesdisposed on an internal circuit card 115, referred to in the art and inthis description as either an “edge card” or a “paddle card.” FIG. 3shows the cable connector 100 without its top portion 116 of theconnector housing 117. Two paddle cards 115 are shown in a stackedformat, one above the other with a predetermined vertical spacing. Thesetwo paddle cards 115 are received in a pair of cards-receiving slots,also not shown, in the opposing mating board connector 102 in order toeffect a connection between the wires 109 and circuits 105 on thecircuit board 104 of the device 106. Thus, as can be appreciated, thepaddle card includes a first end and a second end and includes tracesthat extend between the first and second end. The paddle card typicallyincludes at least one signal layer and one ground layer. It should benoted that the paddle card can be constructed in a convention multilayermanner similar to how conventional circuit boards are manufactured. Thepaddle card can also be formed of a molded dielectric material with asignals traces extending along in one layer (e.g., on one side) andground traces extending along another layer. As can be appreciated, theuse of two or more paddle cards in a stacked arrangement is beneficialfor increasing the density of the connection but is not required.

As shown in FIG. 3, the paddle cards 115 can be seen to have a leadingedge 120 which is received within a card-receiving slot of the matingconnector 106 and as such, the card 115 includes a plurality of contactpads 121 a, 12 b that are arranged in a spaced-apart fashion widthwiseof the card 115. These contact pads are further shown in an arrangementwith a pair of signal contact pads 121 a flanked by two adjacent groundcontact pads 121 b. The cards 115 each have a trailing edge 124 on asecond end that is spaced apart lengthwise of the paddle card 115 andopposite the leading edge 120 on a first end. It is along this trailingedge 124 where a plurality of conductive termination pads 125 arearranged and each such termination pad 125 can be contacted by a singlewire 109 of the cable 108 and attached thereto such as by soldering orthe like.

As illustrated in FIG. 3A, the ground reference plane of the paddle card115 is split into multiple grounds in the form of traces 121 b and thetraces 121 b are configured to engage ground terminals 130 a of theboard connector 106 and which flank the pair of differential signalterminals 130 b. The terminals can be arranged within the boardconnector 102 in repeating G-S-S or G-S-S-G pattern. The groundterminals 130 a of the board connector will typically flank thedifferential signal pair of terminals 130 b and, as such, they willexhibit an affinity to the nearest signal terminal of the signal pair aswell as to the farthest signal terminal of the signal pair. These twoflanking ground terminals 130 a therefore tend to exhibit differentpotentials which may be out of phase.

Regardless of the phase difference, the voltage potential between thetwo grounds creates a signal that can reflect back and forth between theends of the resonant cavity. If a paddle card is provided in the cableconnector 100, the grounds are typically commoned in the paddle cardnear a leading edge of the paddle card (the junction of length B and Cin FIG. 1). Thus, the size of the board connector (length B) tends tolimit the minimum electrical length and the corresponding maximumsignaling frequency that can be used without encountering the resonancecondition. FIG. 3A and 3B, however, illustrate the use of a resistiveelement 148 that couples an intermediate ground plane (ground member 144a) with two different ground traces 121 b. The intermediate ground planeand the ground traces are subsequently commoned together before contactpads 125 are coupled to individual wires.

FIG. 4 illustrates an exemplary embodiment of a paddle card 115 that maybe used in a connector such as connector 100. As can be appreciated,signal pads 121 a, which may be split pads to reduce impedancediscontinuities in the signal path, can be surrounded by ground pads ina G-S-S or G-S-S-G pattern. If the former, a ground member 144 a betweentwo pairs of signal pads may be commoned to two different ground members144 b. The signal pads are coupled with vias 151 to a signal traceprovided on another layer, as discussed below with respect to FIGS. 5A &5B, which depict the paddle card 115 in an exploded view.

As depicted, the paddle card 115 includes a plurality of distinct layersthat are formed in manners well known in the art of circuit boardconstruction. As shown in FIG. 5B, one of the layers 140 includes acircuit trace layer which includes a plurality of conductive traces 150that extend lengthwise between the opposing leading and trailing edgesof the paddle card 115 and which are used to convey signals, preferablydifferential signals across the paddle card 115. These signal traces areshown as terminating in vias 151 that extend through the various layersof the paddle card 115. There is an insulating layer 142 formed of atypical insulative circuit board material such as FR4, or the like, thatlies adjacent to and above the circuit trace layer 140 (as shown inFIGS. 5A & 5B). Lastly, there is a ground plane layer 143 that isdisposed adjacent the insulating layers 142. Other additional layers,including ground layers and/or signal layers, may be provided asdesired.

A shown in FIGS. 4 and 6, the ground plane layer 143 includes a largeground plane 144 that extends lengthwise between the leading andtrailing edges 120, 124 of the paddle card 115. This ground plane 144has a series of lengthwise slots 146 that are formed therein and theslots 146 are spaced apart from each other widthwise of the paddle card115 as they extend generally between the leading edge contact pads 121a, 121 b and the common area 118. As depicted, the common area 118 ispositioned close to the end of the card 120 and is coupled to trailingedge termination pads 125. A series of openings 127 is provided in theground plane 144 and these openings define an area in which the signalcontact pads 121 a are disposed. The signal contact pads 121 a areconnected to the signal traces 150 by the vias 151. The openings 127 maybe considered as encompassing pairs of the signal contact pads 121 a,and providing shielding at the leading edge of the paddle card to eachof the differential signal transmission lines of the paddle card 115.

As shown in FIG. 6, the slots 146 are generally aligned with the sides149 of the openings 127 and they extend proximate to the trailing edgetermination pads 125, but end at the common area 118, which is depictedas close to the rearmost extent or edge 152 along a line “l” (FIG. 5B)that extends transversely to the slots 127. These slots 146 define aseries of individual ground members 144 which extend lengthwise fromwhere the dampening elements are mounted for about a distance of “L” tothe common area of the ground plane members 144. A first set of firstand second ground members are electrically isolated from each on the endthat couples to terminal contacts (which may be positioned along theleading edge 120 of the paddle card 115). These first set of groundmembers 144 a include extension portions that serve as ground contact121 b (and may be pads), while the other set of ground members 144 b endbefore the contacts. In an embodiment, the second set 144 b of groundmembers can define the rear edge 158 or boundary of the opening 127. Thefirst and second set of ground members (or traces) can serve to surroundthe differential signal contact members 121 a on at least three distinctsides of the openings 127. In an embodiment, however, the rear edge 158can also be positioned so that the ground members do not extendsubstantially beyond the dampening elements (e.g., the resistors 148).

Returning to FIG. 1A, and as previously discussed, the potentialdifference on the grounds A and B can vary independently (by skew or byother causes) such that there is a potential difference between them.The potential difference created by the signals passing through theconnector traverses the resonant cavity. When the voltage differencebetween the two grounds is forced into the single ground, a portion ofthe energy is reflected (in other words, it electrically hits a “wall”and bounces back) as an inverted sine wave, shown in the lemniscatelabeled “Without Resonance Damping” in FIG. 1A. This standing wave tendsto degrade the integrity of the signals being transmitted through thistransmission line and can, for example, create mode conversion betweenthe ground and the signal pair.

In an embodiment, an arrangement is provided that dampens thisresonance, and it utilizes a series of dampening elements, preferableresistors that may have a value of 30 ohms, 148 that are applied to thepaddle card 115. The dampening elements 148 may be aligned with eachother along a second line of shorting L2 that also extend transverselyto the slots 146 of the ground plane layer. The electrical length L thatextends between a common area 118, e.g., the rear ends of the slots 146and the point at which the resistive elements are attached to the paddlecard is preferably equivalent to an electrical length that correspondsto about a quarter wavelength of the frequency desired to be reduced.For example, to providing dampening of a resonance condition, theelectrical length L could be configured to be equal to one quarter theassociated separated electrical length of the ground terminals (greaterlengths are effective but tend to increase the length of the connectorwhile providing reduced rates of return from a dampening standpoint).The dampening elements 148 are applied in a manner to the paddle card115 so as to interconnect or couple the individual ground members 144 a,144 b defined by and separated from each other by the intervening slots146.

The dampening elements 148 provide a means for dampening the resonancebecause they absorb energy and dissipate power being carried over theground terminals. For example, when a signal leaves board 5 and travelsthrough connector 10, the signal encounters the dampening elements onthe circuit card 17 and its amplitude is reduced. Depending on theconfiguration, the amplitude of the reflective wave may decreasesignificantly and in some instances, may approach zero. The dampenedwaveform is shown at the bottom of FIG. 1A and is labeled “WithResonance Damping”. The resistive elements 148 may be placed as close aspossible to the contact pads in order to allow to reduce the separatedelectrical length and to help keep the total length of the connector asshort as possible.

FIGS. 7-9C illustrate an alternative embodiment of a resonance dampingarrangement implemented in a connector system. As shown in FIG. 7, aconnector 200 includes a plurality of terminal assemblies 201 shown asinsulative wafers 203 that support a plurality of conductive terminals205. The terminals have contact portions 207 configured to engagecontact portions of an opposing, mating connector (not shown), and theterminals have tail portions 209 (FIG. 8) at opposite ends thereof whichare adapted to fit in through holes or vias 210 on a circuit board 211.The connector 200 has a specific electrical length, measured inpicoseconds, and is equal to the time it takes for a signal to travelfrom the center point of contact of the terminal contact portions 207 tothe center of the terminal tail portion 209 on the opposite end of theterminal. For the discussion to follow, the connector electrical lengthwill be designated Lc and it is shown diagrammatically in FIG. 8. Ifeach terminal is separated from other terminals, then the separatedelectrical length of one of the ground terminals positioned in theconnector 200 is at least Lc. It should be noted that in this style ofconnector, the terminals can be held in discrete sets of signal, groundand function terminals, e.g., certain wafers may support only groundterminals, certain wafers may support only signal terminals and certainwafers may support only functional terminals such as power terminals. Ascan be appreciated, however, such construction is not required.

The connector 200 of the depicted embodiment is a two port connector andis designed to mate with two opposing mating connectors, typically acircuit card mating blade of an electronic module. Other configurations,such as a single port or multiple-port connector, are also contemplated.Thus, the features depicted have applicability to a wide range ofconnector types. In an embodiment, the terminals that extend to eachport are spaced apart from each other in the body of the connector. Thisspaced apart nature can also be provided in the mating circuit board,however for density purposes the vias are typically grouped more tightlyon the circuit board.

As noted above, when separated ground terminal are provided, each groundterminals can have a different potential and, depending on the couplingof the signal terminals to the ground terminals, a significant amount ofenergy can be transmitted over the ground terminals. The potentials thatexist will tend to create reflections and resonances in the connector(as discussed above).

The tails of the terminals are positioned in vias 235 a and are notconnected to the common ground plane. Instead, a trace 221 extends fromthe via 235 a to a via 232 and the via 232 is coupled to the commonground plane. Between the two vias a first contact 227 is provided onthe trace 221 and a second contact 227 is also provided that iselectrically coupled to the first contact by a dampening element 223.The second contact 227 is electrically coupled to a via 235 a, which isalso coupled to the ground plane. Thus, there is a first electricallength h which extends from the via 235 a where the ground is stillseparated from other grounds. However, at the location of the contacts227, a dampened coupling to the ground plane is made. Because theconnector is dampened, it tends to absorb and covert into heat theenergy that might exist due to there being a potential between theground and the ground plane. Furthermore, because this dampened couplingis an electrical distance of l₂, which may be a quarter (¼) of theseparated electrical length of the ground terminal in the connector(which effectively is at least Lc plus L₁), the eventually non-dampenedcoupling between the ground terminal and the ground plane issufficiently distant so as to allow the energy to be absorbed by thedampening element. In other words, since the point of coupling to theground plane via the dampening element is encountered first and theother point of coupling appears to be electrically distant, the energytends to travel through the dampening element. The dampening element,which may be a resistive element, consequently allows the energy todissipate as heat and significantly reduces (or even eliminates) theexcess electrical energy. Thus, the system sees a reduction orelimination of undesirable resonance.

A circuit board may be tuned for a specific connector system bydetermining the separated electrical length of the ground terminals inthe connector and then configuring l₂ or l₄ so that they are about aquarter of the sum of the separated electrical length. It should also benoted that for certain connector designs where the resonance issuesassociated with the separated electrical length of the ground terminalsis/are less pronounced, the electrical length provided by L₂ and l₄ canbe configured for some other frequency of interest.

This same approach can also be accomplished with the traces configuredto provide electrical lengths l₃ and l₄. Thus, as can be appreciated,the traces 221 that couple the ground terminal via 235 a to the via 232that couples the trace to the ground plane in a non-dampened manner canmeander or extend in a relatively straight path. It should be noted thatas depicted, the vias 232 are approximate an edge, such as edge 250. Ascan be appreciated, however, the coupling of the trace to the groundplane need not be positioned near an edge of the circuit board.

It should be noted that the separated electrical length Lc is determinedby the terminal geometry and the average dielectric constant provided bythe corresponding connector and is the time that is takes a signal totraverse the terminal 500 from its contact end 501 to its tail end 502.For example, as shown in FIG. 9D, the electrical length Lc of a surfacemount terminal can be defined as the time that it takes to traverse fromthe center of the terminal contact end 501, shown by endline CLCP inFIG. 9D to the center of the contact pad Lcpad. A through hole terminalis shown in FIG. 9E and the Lc of that terminals can be defined as thetime it takes for the signal to travel from the center of the contactend CLCP to the center of the through-hole tail at a level even with thesurface of the circuit board 106.

Turning now to FIGS. 10-12, another embodiment of a resonance dampingsystem 300 is depicted and it is suitable for use with a surface mountstyle connector. As shown, a connector 302 is mounted to a circuit board304. A paddle card 301 is shown in an installed position but the portionof the connector that would support the paddle card 301 is omitted forpurposes of clarity. As can be appreciated, there are a large number ofvariations in connectors used to support paddle cards and thisdisclosure is not intended to be limited in that respect.

The connector 302 is shown in a simplified manner as additional featurestypically would be used to support the paddle card 301 in position. Forexample, without limitation, multiple rows of terminals could besupported by the connector 302. It should be noted that the connector302 could be configured to support multiple rows of terminals and eachrow would mount on a corresponding row of pads 309 on the circuit board.The connector 302 includes conductive terminals 306 held in aninsulative housing 308. The terminals of the connector 300 arepreconfigured for use as signal or ground terminals, meaning thatcertain ones are assigned to transmit differential signals and others totransmit ground signals. The differential signal terminals are arrangedin pairs of signal terminals and each such terminal pair is typicallyflanked by a pair of ground terminals. The terminals have distinctcontact portions 310 and tail portions 311 disposed at opposite endsthereof and the tail portions 311 in this embodiment include surfacemount feet 312. The terminals 306 can be segregated in groups within theterminals, e.g., the terminals can be arranged in a pattern such as arepeating G-S-S pattern crosswise through the connector.

As noted above, the separated length of a ground terminal is one featurethat is of interest. As a paddle card typically will include a commonground plane over a portion of the paddle card length, the length of theseparated portion of the ground terminal starts from via 301 b where thepaddle card 301 separates into pad 301 a. The paddle card thuscontributes an electrical length l₅ to the total separated electricallength of a particular ground terminal The separated length continuesthrough length l₆, which represents the electrical length of theterminals 306 in the connector 302. The terminal contacts a pad 315 andthe effective separated length of the terminal extends an additionallength l₇ until it reaches a dampening element 348.

As depicted, a primary ground trace 314 and a secondary ground trace 316are associated with each surface mount ground terminal tail portion. Theprimary ground trace 314 extends from conductive contact pad 315. Asdepicted, the primary ground traces 314 extend in a straight line,however it should be noted that a meandering path could also be providedif desired. The secondary ground trace 316 is positioned proximate theprimary ground trace and a gap 317 is provided between the secondaryground trace 316 and the primary ground trace 314 that is bridged by thedampening element 148 (which may be a resistor). As can be appreciated,the circuit board 304 may include a ground plane 318 that is spacedapart from the primary ground trace 314 (as well as the secondary groundtrace 316) by an intervening insulative layer 319. As can beappreciated, additional layers may be added as desired.

A first via 320 couples the secondary ground trace 316 to the groundplane 318 and a second via 321 couples the primary ground trace to theground plane 318. The primary trace 314 may include a contact spur 314 athat is used to couple to the secondary ground trace 316 and an gap 317is provided between them so that a dampening element 348 (such as aresistor) can electrically bridge the gap 317 and electrically couplethe primary ground trace 314 to the secondary ground trace 316. Thedistance between the location of the electrical coupling of the primaryand secondary trace until the second via provides an electrical lengthl₈. The distance may be configured so that the electrical length l₈ (inpicoseconds) is about ¼ the separated electrical length (e.g.,l₅+l₆+l₇). As noted above, however, if the resonance to be dampened isat a higher frequency than that corresponding to the separatedelectrical length then the length l₈ can be further reduced.

The disclosure provided herein describes features in terms of preferredand exemplary embodiments thereof. Numerous other embodiments,modifications and variations within the scope and spirit of the appendedclaims will occur to persons of ordinary skill in the art from a reviewof this disclosure.

We claim:
 1. A resonance damping system, comprising: a circuit board, the circuit board including: a first terminal contact, a first via and a second via and a ground plane, the first and second via coupled the ground plane and the first terminal contact isolated from the ground plane; a first ground trace extending from the first terminal contact to the first via; a second ground trace extending from the second via; and a first dampening element coupling the first ground trace and the second ground trace, the dampening element positioned so as to provide a predetermined electrical length from the dampening element to the first via; and a connector mounted on the circuit board, the connector including a first ground terminal coupled to the first terminal contact, the first ground terminal having an effective separated electrical length.
 2. The system of claim 1, wherein the predetermined electrical length is about one quarter (¼) the effective separated electrical length of the ground terminal.
 3. The system of claim 2, wherein the terminal contact is selected from the group of a contact pad and a through hole.
 4. The system of claim 2, wherein the dampening element is a resistor.
 5. The system of claim 2, further comprising: a second terminal contact, a third via and a fourth via, the third and fourth via coupled the ground plane and the second terminal contact isolated from the ground plane; a third ground trace extending from the second terminal contact to the third via; a fourth ground trace extending from the second fourth via; and a second dampening element coupling the third ground trace and the fourth ground trace, the dampening element positioned so as to provide the predetermined electrical length from the second dampening element to the third via, wherein the connector includes a second ground terminal coupled to the second terminal contact, the second ground terminal having the effective separated electrical length.
 6. The system of claim 5, wherein the connector is mounted on a first side of the circuit board and the first and second dampening elements are positioned on a second side of the circuit board. 